[AT] IH 666 lean / carb

[Chris Britton]

>From: Don Thiel <dwt at rrt.net>
>Subject: [AT] IH 666 runs lean
>.....  I have to have 1/3
>to 1/2 choke on to keep it running.  I have checked the float setting
>and the idle adjustment.  Both are working correctly and no choke is
>required for slow idle, but it still must be choked to keep running
>at fast idle.


Any time I hear 'needs choke to run'  the first 4 things I think of are, 1) 
Too lean a mainjet setting. or 2) a Vacume leak at the carb (halves/throttle 
rod.. etc ) or carb to mainfold or manifold to block/head. or 3) Weak 
sparkies needing the enriched mixture to fire, or 4) partially clogged 
mainjet.. needing that extra manifold vacume to help pull fuel in.. though 
could be an obstruction anywhere in the fuel delivery system also causing 
it.

A reason a carb might idle fine but not run under load is if the idle 
circuit is working fine.. but mainjet is obstructed.

Check the fuel flow to/thru the carb abd bowl.  Check the sparks using a 
spare plug with a wide gap.. ground it to the frame and hook a wire up... 
orange spark won't get it.. under 'no compression' on a battery ignition 
system, you should be able to get just about 3/16" blue spark...

For the vacume leak test, start tractor up and pull outside in open air.. 
throttle it up to where it needs the choke.. but only give it enough to run 
rough.. get a plumbers soldering propane torch.. don't light it.. but turn 
it on.. wave it slowly around the carb and manifold.  The propane from the 
torch should be drawn into any vacume leaks and enrich the mixture. making 
the engine sound change.. probably run smoother.  I've heard of doing that 
test with starting fluid.. however.. i think the propane is way safer.. less 
ignition and explosion hazard.. etc.

Also.. remember.. that weak sparks can be electrical connections.. bad 
switch.. or a bad coil... use jumper wire to jumper around switches to 
check.. etc..

Soundguy